Wash all vegetables thoroughly under cold running water.
Chop tomatoes into large wedges to maintain their interior texture.
Slice the English cucumber into half-moons of approximately 1/4 inch thickness.
Thinly slice the red onion and soak in a bowl of ice-cold water for 5-10 minutes to reduce the sharp bite, then drain and pat dry.
In a small bowl, whisk together extra virgin olive oil, apple cider vinegar, and dried oregano.
Season the vinaigrette with a pinch of sea salt to taste, whisking until slightly emulsified.
Combine the tomatoes, cucumbers, olives, and red onion in a large serving bowl.
Pour the dressing over the vegetables and toss gently to coat.
Top with the block of feta cheese, either left whole or broken into large cubes.
Allow the salad to rest for 10 minutes before serving to let the flavors meld.